WO99/41155 discloses a device for making container blanks by joining opposite wall portions of a material web along connecting portions.
The material web comprises two side wall webs which are passed in a parallel opposite relationship along a manufacturing line and, between them, a bottom wall web folded in two. The webs are thus brought together to a common material web and sealed to each other along said connecting portions by means of heating jaws which engage the material web.
While the heating jaws engage the material web, the web must be kept stationary, which means that the method for producing the container blanks will be intermittent.
The intermittent method of production affects the production capacity which in some cases can be insufficient.
Different solutions for increasing the production capacity have been suggested.
For example, a shaped roller forming a nip together with a back-pressure roller can be used. The material web is passed through the nip, and the shaped roller engages to form said connecting portions. The method allows continuous production of container blanks.
For the container blanks to form liquid-tight containers in the filled state, it is important for the connecting portions to be reliable, i.e. that the sealing process is allowed to take place for a sufficient period of time. To provide this, a plurality of such nips can be arranged in succession, which for obvious reasons requires accurate synchronization and, thus, complicated adjustment.
However, there is a need for an alternative method which allows continuous production of container blanks.